Gordon Brown faced a further blow to his shattered authority last night, as party officials warned that Labour had fared miserably in the EU Parliament elections.

Days after Labour's share of the local election vote slumped to an historic low of 23 per cent it appeared that the party was set for another drubbing in the European elections, held on Thursday.

Party chiefs have resigned themselves to finishing behind the Conservatives and the Liberal Democrats again when the European election results are announced today.

But senior Labour sources last night suggested that the party might even slip to fourth in the national share of the vote, behind the UK Independence Party (Ukip). "A number of minor parties, particularly Ukip, have been benefiting from the fallout from the MPs' expenses scandal," a senior Labour Party official said last night. "We seem to have suffered more than most, as we did in the county council elections last week. The indications are that Ukip have picked up so much that they could even finish second overall."

Sceptics will suggest this is part of the "management of expectations", with Labour hoping that the result will be better – but the mood at senior levels is not hopeful.

The British National Party (BNP) is also expected to increase its vote share. It confidently predicted last week that it would win a seat in the North-west, making its leader, Nick Griffin, the first BNP MEP. But anti-fascist groups claimed last night that the party had not made the advances it had predicted. A spokesman for Searchlight said: "The BNP breakthrough has not happened. They may sneak a seat in the North-west and possibly in the West Midlands, but the sweeping gains that Nick Griffin predicted are not going to materialise."

The Tories are expecting to lead the poll again after local election successes, which leader David Cameron said proved they could win in "every part of the country". Labour lost all of its four councils to the Tories, including Derbyshire, which it held for almost 30 years. The Conservatives also took Devon and Somerset from the Lib Dems and Warwickshire from no overall control, as well as the new Central Bedfordshire and Shropshire unitary authorities. With all the results in from all the 34 councils that held elections, bar one ward, the Tories gained 233 councillors while Labour lost 273 seats and the Lib Dems four.

Mr Cameron said Labour's collapse demonstrated that voters wanted a "strong, positive and united alternative" government – and he claimed his party represented that alternative. He added: "We have won almost every council we could possibly have won... We have won councils we really did not think we were going to win."

With counting almost complete, projections suggested the Conservatives won 38 per cent of the national vote, and the Lib Dems 28 per cent, ahead of Labour on 23 per cent. Other parties took 11 per cent. Labour lost a total of 273 councillors, the Lib Dems lost four and the Tories gained 233 seats. Meanwhile, the Green Party won 16 seats while Ukip picked up six, including three in Staffordshire. The BNP won three seats – in Lancashire, Leicestershire and Hertfordshire.

Turnout was mixed, with areas varying between 30 to 45 per cent – generally lower than the last time these councils were fought on general election day in 2005. However, the share of the vote in comparison to previous years offered a crumb of comfort for Labour, as it showed the Tories were not as far ahead as previously suggested. The official rundown showed both the Tories and Lib Dems had matched their performance in local elections in 2004. Labour was three points down on its share then, which came a year before the party won the General Election.

But the Tories' vote was significantly down on the 44 per cent achieved a year ago. There were some suggestions that the party's vote fell in areas where the local MP had been caught up in the expenses scandal.

Lib Dem leader Nick Clegg, hailing "spectacular gains" in Bristol, said this was the beginning of a "complete transformation of city politics" with his party taking urban seats off Labour. But he admitted it looked like the Lib Dems were facing a strong challenge from the Tories in the rural South-west.

Winners and losers: What the parties can expect from tonight's results

Labour

Gordon Brown presided over a slump to an all-time low of 23 per cent in the county council elections, held on the same day as the European elections last Thursday; anything less than that would push him close to full-blown crisis. The latest predictions suggest Labour's share of the vote could slump to 18 per cent, reducing its number of MEPs from 19 to 15. Even with the plethora of smaller parties competing for votes, that would be difficult to defend.

Conservatives

Michael Howard led the Tories to victory in these elections in 2004 with 26.7 per cent of the vote, so David Cameron must at least match that. The party is expected to poll marginally more, although the overall reduction in UK seats would still cut the Tory representation from 27 to 24. Closer to 30 per cent would see Mr Cameron as a near-certainty to win the next general election.

Liberal Democrats

Nick Clegg must also at least match his predecessor's performance to satisfy colleagues he is moving in the right direction. Charles Kennedy polled just under 15 per cent in 2004, sending 12 MEPs to Brussels. This time, polls suggest the Lib Dems could win a marginally higher share of the vote.

Ukip

A notable third in 2004, but could go one better this time around. Ukip's share of the vote in 2004 was 16.1 per cent and the party is still expected to do well enough to maintain its standing, comfortably ahead of the Lib Dems again.

Greens

Squeezed by the Ukip surge in 2004, the Greens could be on the march this time, aided by disillusionment with the major parties. They polled only 6.3 per cent of the vote last time but are expected to almost double that, giving them six MEPs, up from two.